Tap chamfering machine



July 23, 1940. JUDGE TAP d'HAMi-ERiNG MACHINE 4 Sheets-Sheet 1 Filed Aug. 18, 1958 Fran 61. F

4 Sheets-Sheet 2 Filed Aug. 18, 1938 July 23, 1940. F, JUDGE 2,209,228

TAP CHAMFERING MACHINE Filed Aug. 18, 1938 4 Sheets-Sheet 3 a9 w 53 J02- 51 p J6 July 23, 1940. JUDGE 2,209,228

TAP CHAMFERING MACHINE Filed Aug. 18, 1938 4 Sheets-Sheet 4 71 75', r54 L a f -.94

b mmzm W e Win-aw Patented July 23, 1940 TAP CHAMFEBING MACHINE Franklin Judge, Greenfield, Mass.

Application August. 18,

2' Claims.

This invention relates to a machine particularly designed for grinding the entrance taper or chamfer angle at the ends of the lands of a thread-cutting tap.

This chamfered entering end portion of a tap is subject to more rapid wear than any other portion of the tap and requires more frequent regrinding. It is also desirable that all of the lands of a p be ground to identical contours, so that any endency of the tap to cut off-center may be avoided. Machines heretofore developed for this particular purpose have been of complicated construction and have not been readily adapted for use with differing kinds of taps.

It is the general object of my invention to provide an improved machine for chamfering taps and for performing other similar operations,

by which such operations may be quickly, easily and accurately performed.

A further object is toprovide a machine which is relatively simple in construction, economical in manufacture, and easily adapted for use with taps having different numbers of flutes, different angles of chamfer, or different relief angles.

My invention further relates to arrangements and combinations of parts which will be hereinafter described and more particularly pointed out in the appended claims.

A preferred form of the invention is shown in the drawings, in which Fig. l is a plan view, partly in section, of my improved tap chamfering machine;

Fig. 2 is a front elevation thereof, looking in the direction of the arrow 2 in Fig. 1;

Fig. 3 is an end view of certain parts, looking in the direction of the arrow 3 in Fig. 1;

Fig. 4 is a sectional end elevation, taken along the irregular line 4-4 in Fig. 2;

Figs. 5 and 6 are detail sectional views, taken along the lines 5-5 and 6--5 in Fig. 1;

Fig. 7 is a front elevation of a modified tap support; and

Fig. 8 is a detail view to be described.

I Referring to the drawings, my improved tap chamfering machine comprises a grinding portion A and a tap supporting and rotating portion B, both assembled on a main base It.

The portion A preferably comprises a motor M having a grinding wheel W mounted on the armature shaft thereof. The wheel W may desirably be recessed, as indicated at II in Fig. 2, to receive a clamping bolt I2 and a washer l3. A casing or guard 14 surrounds the wheel W and is supported on the base portion [5 of the motor M. The guard I4 is recessed at H (Fig. 4) to clear certain of the tap supporting parts.

The motor base 15 is mounted on a wheel slide 20, having a dove-tail portion 2| (Fig. 2) slidable in guideways in a wheel table 22. The table 22 is pivoted at 23 to the base It) and is 1938, Serial No. 225,601

angularly adjustable about said pivot. The axis of the pivot 23. is substantially in transverse alignment with the axis of the tap to be ground. Clamps 24 (Fig. 1) are provided for holding the table 22 in angularly adjusted position.

A cross feed screw 30 (Fig. 4) is rotatably mounted in a bearing in the table 22 but is restrained from axial movement therein. The screw 30 is threaded in a nut 32 secured to the under side of the wheel slide 20. A handle 33 (Fig. 1) is provided for turning the cross feed screw 30 and thus adjusting the motor M and wheel W toward or away from the tap.

A truing device 35 (Fig. 4) is slidably mounted in a guideway 36 fixed at the rear of the wheel slide 20 and may be moved axially of the wheel by means of a handle 31 to dress the cylindrical outer surface thereof.

The usual electrical connections are provided for the motor M, and said motor may be controlled by a switch S (Fig. 2) mounted on the front of the motor base I5.

By the constructions described, the grinding wheel may be adjusted with its peripheral surface at any desired angle to the axis of the tap, so as to provide any desired chamfer angle, and may be adjusted forward or rearward to grind taps of different diameters.

I will now describe the tap supporting and rotating portion B of my improved machine. This portionrcomprises a work head 40 (Fig. 3) slidable in guideways M in a raised end portion of the base it. The head 40 may be clamped in adjusted position by gib screws 42 (Fig. 1)

The tap T (Fig. to be chamfered may be held in a draw-back chuck 50 (Fig. 1) mounted in a chuck spindle 52, which in turn is rotatably mounted in bearings in the upper portion of a work support 54. The support 54 is mounted to rock or swing on a cross shaft 55 (Fig. 2) supported in bearings 56 on the work head 40. The draw-back chuck 50 may be of any usual or commercial construction and may be tightened or loosened by use of a hand wheel 51 (Fig. 1).

In chamfering taps, it is necessary not only to grind the ends of the lands at the desired angle, but also to separately back off or relieve each land of the tap as the chamfer is ground, for the purpose of clearance. 4

I accomplish this relieving action by swinging or oscillating the work support 54 on the cross shaft 55 during the grinding operation, and I have provided specially designed mechanism for rotating the tap and. for oscillating the work support in predetermined timed relation to such rotation.

For this purpose, I connect the chuck spindle 52 through gears fill, GI and 52 (Fig. 1) to an operating shaft 64 rotatably mounted in the work support 54 and having means, such as a hand by a clamping screw 61 (Kg. 3).

A spacing collar 60 is provided on the chuck spindle 52, and the gear and collar 00 may be interchanged when compound gearing is necessary to secure a'desired ratio.

A two-to-one ratio between the revolutions of the operatingshaft 64 and of the chuck spindle I! is required for two-flute taps and may be easily attained by simple gearing, but compound gearing is usually desirable for the three-to-one' or four-to-one reductions required when grinding three-flute or four-flute taps.

I obtain the desired oscillating movement of the work support 54 by providing the left-hand end of the operating shaft 64 (as viewed in Fig.

-1) with a disc fixed thereon and carrying a pair of adjusting screws II (Fig. 6). A second disc 12 (Fig. 1) is secured to the disc III by a pivot screw I4 (Fig. 6) and also by a clamping screw extending through a slot 16 in the disc I0. Angular adjustmentof the disc 12 relative to the disc I0 is eflfected by engagement of the I screws II with the shank of the screw I5.

' The outer and adjustable disc I2 has a pivot stud 00 mounted therein and connected by a link ll (Fig. 1) to a fixed pivot stud 82 in a post or stand 83 (Fig. 3) mounted on the work ahead 40. By adjustment of the disc 12, the pivot stud 00 may be thrown ofi' center with respect to the axis of the disc 10 and the operating shaft 64.

When the shaft 84 is subsequently rotated, the pivot stud so will have an eccentric motion and will react against the link 81 which is' mounted on a fixed pivot. This will thus produce a limited oscillating or swinging movement of the work support SI. The amount of this movement is determined by the adjustment of the disc 12 by the screws II, and the eccentricity is shown by graduations on the disc 10 (Fig. 1) relative to an index mark on the disc 12. Each space on the scale will commonly indicate 0.003" relief.

Through the described mechanism, the chuck spindle 52 is moved toward and from the grinding wheel in timed relation to its rotation. The

- change gearing is so selected as to swing the chuck 50 and tap T toward the wheel for backingofi. action each time a land is being ground-and to swing the tap away from the wheel as each space a (Fig. 5) between two lands passes the grinding point.

In order that the backing of! or relieving shall be accurately correlated to the lands, I provide the tap setting device shown in Figs. 1 and 5. This device comprises a gauge or stop 90 mounted in the end of a plunger SI axially movable but non-rotatable in a supporting bar 92 slidably mounted on the work support 54 and held in desired position by a clamping screw (Fig 1).

When a tap T (Fig. 5) is inserted in the chuck 50, the plunger Si ispushed inward so that the cutting edge of a land may be' pressed against said stop or gauge. At the same time the shaft II is tln'ned to bring an index line b (Fig. 8) in line with an index plate 04 on the work support II, the tap T being then at its point of farthest removal from the wheel W. V

After the tap is clamped in its adjusted position, the plunger 9| is released and the gauge 00- moves back where it will not be engaged by the tap during subsequent rotation thereof. The grinding wheel W is then moved forward by the cross feed screw to produce the desired amount of chamfer and the chamfering and relieving operation is then performed .as described.

It is at times desirable to support a tap on centers during the chamfering operation, instead of holding the tap in a chuck, and for this purpose I provide the attachment shown in Fig. 7. This comprises an arm I00 supporting a tail center IM and fixed on a rod I02 which is slidable in the work support and may be secured in adjustment position therein by a binding screw I03.

The rod I02 is preferably keyed in the support 5| so that the center "I will be held in axial alignment with a second center I04 held in the draw back chuck. The tap T may be caused to rotate with the chuck and chuck spindle by a dog I 05 engaging a suitable notch or projection in the end of the chuck or chuck spindle.

It occasionally happens that the lands of a tap are irregularly spaced angularly, and in such a case the tap may be accurately ground by resetting the tap by means of the stop or gauge 00 before each land is ground.

It will be evident from the foregoing description that my improved machine, while of very simple construction, is well adapted for its intended purposes and that it is also very easily set and adjusted for chambering taps having widely differing characteristics, The machine may also be used for other and somewhat general purposes.

Having thus described my invention and the advantages thereof, I do not wish to be limited to the details herein disclosed, otherwise than as set forth in the claims, but what I claim is:

1. A grindingmachine comprising a grinding wheel, means to rotate said wheel in a defined position, a support for the work mounted to swing about an axis parallel to the axis of rota tion of the work, a shaft mounted in said'work support and connected to rotate the work, a link connecting an eccentric element on said shaft to a fixed pivot to give the work a predetermined number of swinging movements about said axis parallel to the axis of rotation of the work and about said axis parallel to the axis of rotation of said tap and toward and from the grinding surface of the wheel during each revolution of said tap, said oscillations being equal in number to the lands of the tap, and said latter means including a stud having an eccentric motion about an axis in said work support parallel to the axis of rotation of the tap and rotated in fixed speed relation to the rotation of the tap, and a link connecting said stud to a fixed pivot. 1

' JUDGE; 

